Could it be small particles of suspended sand or other debris being shook up by the Eel or other inhabitants? If so there's not much you can do except beef up the mechanical filtration and clean it often.
, 65 lbs Fiji LR
, 4" Aragamax DSB
, Coralife 2X96w CF
, CPR Bakpak II, CPR Aquafuge 12 w/ 2x9 Coralife Mini Aqualight, 4 Maxijet 600's, PCI 200W Titanium Heater, 2 Blue Green Chromis, 1 Gold Bar Maroon Clown, 1 Purple-Stripe Dottyback, Finger Leather, Trumpets, Rose Coral Open-Brain, Pagoda Cup, Xenia, Star Polyps, Yellow Polyps, Various Mushrooms, Toadstool Leather, 12 Astraea, 10 Nassarius, 4 Bumble Bee, 6 Cerith Snails, 12 Red Tip Hermits.